It is well known to conference two or more PCM signals by comparing the signals (ignoring the sign bit), the highest amplitude being passed through to the output. This method is known as the `Highest Amplitude Wins` method. This occurs at the PCM word rate (8 kHz) and so can rapidly switch between sources. The argument for this approach is that when two people speak simultaneously in a conference call, it is difficult to distinguish one person from the other. Thus any additional distortion due to the rapid switching does not make the situation worse. Hence conferencing two PCM words is effected by simultaneous comparison, whereafter the larger word is transmitted to the listener.
A problem with this method is that while the primary speaker talks, inflections in speech could be lower in amplitude than background noise from the other conferenced channel. Hence the resultant speech has `glitches` which, in effect, increases back- ground noise in the resultant conferenced signal An object of the invention is to provide a conferencing arrangement in which this difficulty is minimised or overcome.